1. Field of Invention
The present invention relates to a paper binder, and more particularly to a binder unit for binding a stack sheet, wherein the binder unit provides a one-piece structure to securely hold the edge portion of the bundle of sheets through the holes thereof.
2. Description of Related Arts
A paper binder is considered as one of the common tools to hold several sheets of paper together. It is usually commonly used in office. People widely uses in its small, light, quick, and easily removed. Accordingly, there are two major types of conventional paper binder, which are hole-punching type and non-hole-punching type.
The non-hole-punching type of paper binder consists of paper clip, binder clip, and staples for holding bounce of paper together without punching any hole on the paper. The paper clip is a device which holds several sheets of paper together by means of pressure. It leaves the paper intact and can be quickly and easily removed. However, the paper clips must be configured in different sizes to fit the corresponding thickness of the paper stack. In other words, when more sheets of paper are gradually accumulated to increase the thickness of the paper stack, the user must change a bigger size of paper clip to hold the paper stack tightly.
Furthermore, the paper clip is a thin wire bent into a looped shape that takes advantage of the elasticity and strength of the material of its construction. However, the paper clip is extremely easy to be deformed its shape to loss the clip) ability of the paper clip. In other words, the paper clip is a good tool for the user to temporary hold the paper together, but it is not a secure way to put our important document together.
The binder clip is commonly used in the modern office, and is also a simple device for binding a few to many sheets of paper. In the same way, it leaves the paper intact and can be quickly and easily removed. As compared to a paper clip, the binder clip is able to bind sheets of paper more securely, and is also resistant to rust. But there are still several sizes of binder clips to meet the customers need in responsive to the thickness of the paper stack. Moreover, owing to the arm of force of the binder clip is usually small, people often need to apply huge force to allow the clip to be open. Furthermore, if there are only few sheets of paper for being held together, the binder clip is not usually function well. Thus, the size of the binder clip is relatively large that the binder clip will normally take the whole corner portion of the paper stack.
The staple is another way to hold a bunch of paper together. The legs of the stable are penetrated through the paper stack to the back side thereof and are folded over to provide greater binding that the friction of straight legs. It keeps the advantages of easily operating and secure. However, the staple will damage the paper stack especially when the staple is removed from the paper stack. Thus, the staple cannot be re-used.
The hole-punching type of paper binder requires two or more spaced apart holes punched on each of the paper to form a punching hole such that when the papers are stacked, the punching holes of the papers are aligned to form two spaced apart mounting holes for the paper binder binding thereat. Accordingly, such paper binder can securely hold the paper stack in position through the mounting hole especially for lots of papers stacking together. The paper binder generally comprises a base clip with two flexible arms extending through the mounting holes from the back side of the paper stack and a front clip coupling with the flexible arms at the front side of the paper stack. However, each of the punching holes of the paper is extremely easy to be damaged because the flexible arm may cut at the circumferential edge of the punching hole during binding operation. Thus, some hole-punching type of paper binders require two mounting holes to bind the papers while some hole-punching type of paper binders require three mounting hole to bind the papers. However, the particular configuration of the paper binder can only work with either the two-hole paper or the three-hole paper only.
Accordingly, the major drawback of the hole-punching type of paper binder is that once the papers are bound together, the user must take out the whole stack of papers to select the particular sheet of paper. In other words, when the user take out the whole stack of papers from the paper binder, the punching holes of the papers are not aligned anymore. Therefore, after the user takes the particular sheet of paper from the paper stack, he or she must align the punching holes of the papers again for the flexible arm passing therethrough. As it is mentioned above, the flexible arm may cut at the circumferential edge of the punching hole during binding operation.